Simple Daydream controller shake / direction detection. Modified from Daydream sample controller code and a low pass filter example I found on stack overflow

Controller.cs

using UnityEngine;
using System.Collections;

public class Controller : MonoBehaviour {
	public GameObject controllerPivot;

	public float accelerometerUpdateInterval = 1f / 60f;
	public float lowPassKernelWidthInSeconds = 1f;
	public float shakeDetectionThreshold = 2f;

	public float minShakeTime = .1f;

	float _lowPassFilterFactor;
	Vector3 _lowPassValue;
	Vector3 _acceleration;
	Vector3 _deltaAcceleration;

	float _shakeTimeStamp;

	// Use this for initialization
	void Start () { 

		_lowPassFilterFactor = accelerometerUpdateInterval / lowPassKernelWidthInSeconds;
		_lowPassValue = Vector3.zero;

		shakeDetectionThreshold *= shakeDetectionThreshold;
		_lowPassValue = GvrController.Accel;
	}

	// Update is called once per frame
	void Update() {
		UpdatePointer();
		UpdateAcceleration ();

	}

	void UpdateAcceleration() {

		if (Time.time < (_shakeTimeStamp + minShakeTime)) {
			_lowPassValue = Vector3.zero;
			return;
		}

		_acceleration = GvrController.Accel;
		_lowPassValue = Vector3.Lerp (_lowPassValue, _acceleration, _lowPassFilterFactor);
		_deltaAcceleration = _acceleration - _lowPassValue;

		if (_deltaAcceleration.magnitude >= shakeDetectionThreshold) {

			Debug.Log ("SHAKE!!!!! " + _deltaAcceleration.ToString () + " : " + Time.time);

			if (Vector3.Angle (Vector3.up, _deltaAcceleration) <= 25f) {
				Debug.Log ("SHAKE UP!");
			} 
			else if (Vector3.Angle (Vector3.down, _deltaAcceleration) <= 25f) {
				Debug.Log ("SHAKE DOWN!");
			}
			else if (Vector3.Angle (Camera.main.transform.right, _deltaAcceleration) <= 25f) {
				Debug.Log ("SHAKE RIGHT!");
			}
			else if (Vector3.Angle (-Camera.main.transform.right, _deltaAcceleration) <= 25f) {
				Debug.Log ("SHAKE LEFT!");
			}
				
			_shakeTimeStamp = Time.time;
		}
	}

	private void UpdatePointer() {
		if (GvrController.State != GvrConnectionState.Connected) {
			controllerPivot.SetActive(false);
		}

		controllerPivot.SetActive(true);
		controllerPivot.transform.rotation = GvrController.Orientation;
	}
}